Passage cave

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Quackenschloss , a through cave in Franconian Switzerland near Engelhardsberg, Upper Franconia, Bavaria.

A through cave is a cave that has a natural entrance and exit. If a cave reaches a certain size, it usually has several entrances, so that it almost inevitably falls into this category. Thus, the longest cave in the world, the Mammoth Cave in Mammoth Cave National Park in Kentucky , USA , is also the longest through cave .

The term only makes sense in certain karst areas of the world where caves are only small in size or, due to the hydrogeological situation, typically only have one exit. In this case, a through cave is a special feature.

One such karst area is the Swabian Alb , in which caves are mostly small-scale. The large active water caves on the lowest karst floor, such as the Falkensteiner Cave or the Mordloch , do not have a second entrance. The entrance is actually the end of the cave, the outflow of the water into a valley. From there the cave ascends and becomes smaller and smaller into the mountain. The cover is so thick that there is no further entrance. The water penetrates the karst body through clefts and narrow crevices and then collects in the water cave.

In the course of exploring a cave, it can at some point achieve the characteristics of a through cave, namely when a second entrance is discovered. A well-known example is the Blautopfhöhle , which only became a through cave after many years of exploration through the discovery of the connection to the Vetterhöhle in 2006. In such a case, both caves usually had their own names. A new name was needed for the entire system. If a cave is significantly larger, its name can be adopted for the system; if both are important, double names are formed. It is also common to add the ending system (example: blue cave system ) or to assign a new name.

In addition to the size of the cave, the degree of maturity is also decisive for the number of through caves. If the cover becomes smaller and the cave larger at the same time, collapses ( sinkholes ) occur more frequently and the cave becomes a through cave. If poljes are formed , which are collapsed cave parts, these are connected by remains of the former cave, which are therefore caves through. This is even more extreme in tropical karst areas, in cone or cockpit karst . Only remnants of the limestone are preserved there, through which the ruins of the former cave systems cross .

The name is a morphological description of the cave, not a geological one . The term through cave has little geological meaning either, it is a very important morphological property, especially when it is a large horizontal cave. Such caves are often used as connecting routes and also as natural tunnels for roads or railways.

Examples